878 COCO 



dtvolouri.se it entirely. The first process, -which is very good in the hands of a skilful 

 chemist, does not appear to us to be a convenient method for the consumer ; in tho 

 first place, it is difficult to procure perfectly identical solutions; in the next place, it is 

 impossible to keep them a long time -without alteration. We know that chlorine 

 dissolved in -water reacts, oven in diffused light, on this liquid ; decomposes it, appro- 

 priates its elements, and gives rise to some compounds which possess an action quite 

 different from that of the chlorine solution in its primitive state. The second process 

 seems to us to be preferable, as the proof liquor may be kept a long while without 

 alteration. A graduated tube is also used ; each division represents one hundredth of 

 the colouring matter. Thus tho quantity of proof liquor added exactly represents 

 the quantity in hundredths of colouring matter contained in the decoction of cochineal 

 which has been submitted to examination. The following remarks from a practical 

 dyer are valuable : 



' The colouring matter of cochineal being soluble in water, I have used this solvent 

 for exhausting the different kinds which I have submitted to examination in tho 

 colourimeter. I operated in the following manner : I took a grain of each of the 

 cochineals to be tried, dried at 120 Fahr. ; I submitted them five consecutive times to 

 the action of 200 grains of distilled water at -water-bath heat, each time for an hour ; 

 for every 200 grains of distilled water I added two drops of a concentrated solution of 

 acid sulphate of alumina and of potash. This addition is necessary to obtain the 

 decoctions of the different cochineals exactly of the same tint, in order to be able 

 to compare the intensity of the tints in the colourimeter. 1 



' In order to estimate a cochineal in the colourimeter, two solutions, obtained as 

 described above, are taken ; some of these solutions are introduced into the colouri- 

 metric tubes as far as zero of the scale, which is equivalent to 100 parts of the superior 

 scale ; these tubes are placed in the box, and the tint of the liquids enclosed is com- 

 pared by looking at the two tubes through the eye-hole ; the box being placed so that 

 the light falls exactly on the extremity where the tubes are. If a difference of tint 

 is observed between the two liquors, water is added to the darkest (which is always 

 that of the cochineal taken as type) until the tubes appear of the same tint. 2 



' The number of parts of liquor which are contained in the tube to which water has 

 been added is then read off; this number, compared with tho volume of the liquor 

 contained in the other tube, a volume which has not been changed, and is equal to 

 100, indicates the relation between the colouring power and the relative quality of 

 the two cochineals. And if, for example, 60 parts of water must be added to the 

 liquor of good cochineal, to bring it to the same tint as the other, the relation of 

 volume of the liquids contained in the tubes will be in the case as 160 is to 100, and 

 the relative quality of the cochineals will be represented by tho same relation, since 

 the quality of the samples tried is in proportion to their colouring power.' Napier. 



The exports from Guatemala consist principally of cochineal, the staple and 

 almost the only article of exportation for a number of years past. It is chiefly pro- 

 duced in Old Guatemala, nine leagues distant from Guatemala, and also in Amatellan 

 about six leagues distant. The rearing of this insect is subject to so many accidents 

 and contingencies that it is excessively precarious, and, above all, the weather has a 

 great effect upon it. Taking all this into consideration it is surprising that attention 

 has not been directed to the cultivation and production of other articles suited to the 

 dimate and soil of Guatemala, and less liable to destruction by unseasonable rains 

 and atmospheric changes than cochineal. It is reasonably to be feared that, if a 

 longer time be suffered to pass, the cochineal of this country cannot compete with that 

 of Teneriffe, and other parts of the world, where it is now cultivated. 

 Our Imports of cochineal have been as follow : 



In 1870 we imported 47,790 cwts., valued at 581,956. 



1871 54,642 706,713. 



1872 38,160 494,541. 



COCK-METAIi. An inferior metal ; a mixture of copper and lead used for 

 making cocks. See Aixoy. 



COCO. A species of Aracece, to which the genus Arum gives the name. The 

 rhizomes or underground stems of the cocos (Colocasea) are sometimes substituted for 

 potatoes and yams ; they abound in starchy matter. 



1 Care must be taken not to add to tho water, which serves to extract the colouring matter from 

 the different cochineals, more than the requisite quantity of acid sulphate of alumina and solution of 

 potash, because a stronger dose would precipitate a part of the colouring matter in the state of lake. 



* For diluting the liquors the same water must always be used which has served to extract the 

 colouring matter of the cochineals under examination, otherwise the darkest decoction would pass 

 into violet, as water was added to it, to bring back tho tint to the same degree of intensity as 

 that of the decoction to which it is compared. 



